The purification and characterization of the properties of adenosylmethionine (AdoMet) synthetase are being pursued further. AdoMet synthase from yeast are inhibited by cycloleucine, L-methionine methyl ester, L-methionine ethyl ester, and L-methionine t-butyl ester. 3-Deazaadenosylmethionine stimulates the tripolyphosphatase (PPPase) activity of AdoMet synthetase while it also enchances the steady state rate of AdoMet synthetase. Although guanosylmethionine and cytidylmethionine can also stimulate the PPPase to a lesser extent, they are ineffective in enhancing the steady state rate of AdoMet synthetase.